A mother who left her children - aged four and two - home alone in a flat for nearly eight hours was arrested by police yesterday for alleged child cruelty.

Police went to the woman's flat at Shing Wui Court, in Tin Shui Wai, just before 2am after receiving a report from neighbours that children were crying loudly inside.

Officers rang the doorbell and the door was opened by the four-year-old boy, who was found crying with his younger sister. No one else was inside the flat and the children both had bruises on their bodies, police said.

Police stayed with the children until their 26-year-old mother returned home with a woman friend at 2.30am. She told police she had been doing last-minute Lunar New Year shopping.

After being questioned, she was arrested for alleged cruelty to her children.

The children were admitted to Tuen Mun Hospital for observation. They remained in hospital last night.

Police released their mother on $500 bail and ordered her to report back to police on February 28.

Police said the mother, a single parent, went out with her girlfriend at 7pm on Wednesday, leaving her children alone in the flat.

The case has been referred to the Social Welfare Department to determine if the children can be returned to their mother.